1. Field of the Invention
The present invention relates to a method of producing an electroconductive cellulose-based film. The electroconductive cellulose-based film, which in various optical films, is used as a hard coating film having a hard coating layer formed thereon and an anti-reflection film having an anti-reflection layer formed thereon. For example, the film applied to an optical element such as a polarizing plate etc. can be utilized preferably in various image displays such as a liquid crystal display, organic EL display, PDP and CRT. The film can also be used preferably as a constituent member or an attachment member in a polarizing filter, an anti-reflection filter etc.
2. Description of the Related Art
Owing to research and development in recent years, a liquid crystal display panel comes to secure a firm position as display. However, a car-navigation monitor or a video-camera monitor which is used highly frequently under high illumination undergoes a significant reduction in visibility and recognizability because of occurrence of surface reflection. Accordingly, it comes to be essential that a polarizing plate used in the liquid crystal display panel be subjected to with anti-reflection treatment, and the polarizing plate subjected to anti-reflection treatment is used in almost all liquid crystal displays used frequently outdoors.
The anti-reflection treatment is designed so as to achieve the maximum reduction in the reflection, in the visible light range, of a multilayer laminate of plural films made of materials different in refractive index which is prepared generally by a dry process such as vacuum deposition, sputtering and CVD or by a wet process using a die or a gravure roil coater. Particularly, the wet process is used preferably because the cost of facilities is low, a film of large area can be continuously produced, and the process is excellent in productivity.
In the wet process, however, a small amount of water may be mixed in a coating solution in the coating operation, in preparation of the coating solution, and depending on the humidity of an atmosphere for storage. In this case, there has been a problem that a lower boiling organic solvent in the organic solvent starts evaporation in a drying step after application of the coating solution so that as the evaporation proceeds, the solubility of water in the organic solvent reaches a saturation state to cause phase separation, and during this process, hydrophilic superfine particles are transferred predominantly to the aqueous phase where they are aggregated to cause bleaching, thus significantly deteriorating optical properties such as transmittance.